Method of producing a higher-purity metal

ABSTRACT

A method of producing a higher purity metal comprising the step of electrolyzing a coarse metal material by a primary electrolysis to obtain a primary electrodeposited metal, the step of electrolyzing the material with the primary electrodeposited metal obtained in the primary electrolysis step used as an anode to obtain a higher purity electrolyte for secondary electrolysis, and the step of further performing secondary electrolysis by employing higher purity electrolytic solution than said electrolytic solution with said primary electrodeposited metal as an anode, whereby providing an electro-refining method that effectively uses electrodes and an electrolyte produced in a plurality of electro-refining steps, reuses the flow of an electrolyte in the system, reduces organic matter-caused oxygen content, and can effectively produce a high purity metal.

TECHNICAL FIELD

[0001] The present invention relates to a method of producing higherpurity metal which effectively uses electrodes and an electrolyteproduced in a plurality of electrolytic steps, and performs primaryelectrolysis and secondary electrolysis, and, when necessary, tertiaryelectrolysis of reusing the flow of an electrolyte in the system.

[0002] Moreover, the present invention further relates to a method ofhigher purification effective in the higher purification of metal whichreduces the oxygen content caused by organic matter.

[0003] Further, the present invention additionally relates to a methodof producing a higher purity metal in which, among the metals to beproduced in a higher purity pursuant to the foregoing methods, the totalcontent of alkali metal elements such as Na, K is 1 ppm or less; thetotal content of radio active elements such as U, Th is 1 ppb or less;the total content of transition metal or heavy metal elements such asFe, Ni, Cr, Cu, excluding cases of being contained as the principalcomponent, is 10 ppm or less; and the remaining portion thereof becomesa higher purity metal or other indispensable impurities.

[0004] In addition, the %, ppm, ppb used in the present specificationall refer to wt %, wtppm, wtppb.

BACKGROUND ART

[0005] Conventionally, when producing a 4N or 5N (respectively implying99.99 wt %, 99.999 wt %) level higher purity metal, the electro-refiningmethod is often employed for the production thereof. Nevertheless, thereare many cases where approximate elements remain as impurities whenperforming electrolysis to the target metal. For example, in the case ofa transition metal such as iron, numerous elements such as nickel,cobalt and so on, which are also transition metals, are contained asimpurities.

[0006] When refining such crude metals of a 3N level, electrolysis isperformed upon producing a higher purity liquid.

[0007] In order to obtain a higher purity metal in the foregoingelectrolysis, it is necessary to employ a method of ion exchange orsolvent extraction for producing an electrolytic solution with fewimpurities.

[0008] As described above, the production of an electrolytic solutionnormally requires a refinement in advance prior to the electrolysis, andhas a shortcoming in that the production cost therefor would becomehigh.

DISCLOSURE OF THE INVENTION

[0009] An object of the present invention is to provide an electrolysismethod which effectively uses electrodes and an electrolyte produced ina plurality of electrolytic steps, reuses the flow of an electrolyticsolution in the system, and thereby enables the effective production ofa higher purity metal. Another object of the present invention is tofurther provide a method of producing a higher purity metal whicheffectively uses electrodes and an electrolyte produced in a pluralityof electrolytic steps, reuses the flow of an electrolytic solution inthe system, reduces organic matter-caused oxygen content, and therebyenables the effective production of a higher purity metal.

[0010] In order to achieve the foregoing objects, it has been discoveredthat by using an electrolytic solution, which was electrolyzed with theprimary electrodeposited metal obtained by the primary electrolytic stepas the anode, for the secondary electrolysis, the preparation of theelectrolytic solution can be simplified, and a higher purity metal canbe obtained pursuant to a plurality of electrolytic steps. In addition,by washing the electrolytic solution used above, the oxygen contentcaused by organic matter can be reduced.

[0011] Based on the foregoing discovery, the present invention provides:

[0012] 1. A method of producing a higher purity metal comprising thestep of electrolyzing a coarse metal material by primary electrolysis toobtain a primary electrodeposited metal, the step of performingelectrochemical dissolution with the primary electrodeposited metalobtained in the primary electrolysis step as an anode or performing aciddissolution to the primary electrodeposited metal in order to obtain ahigher purity electrolytic solution for secondary electrolysis, and thestep of further performing secondary electrolysis by employing saidhigher purity electrolytic solution for secondary electrolysis with saidprimary electrodeposited metal as an anode;

[0013] 2. A method of producing a higher purity metal comprising thestep of electrolyzing a coarse metal material by primary electrolysis toobtain a primary electrodeposited metal, the step of obtaining a higherpurity electrolytic solution for secondary electrolysis by performingelectrochemical dissolution or acid dissolution with the primaryelectrodeposited metal obtained in the primary electrolysis step as ananode, and the step of further performing secondary electrolysis byemploying said higher purity electrolytic solution for secondaryelectrolysis with said primary electrodeposited metal as an anode,wherein said electrolytic solution is liquid-circulated in an activatedcarbon tank in order to eliminate organic matter in the higher puritymetal aqueous solution, thereby reducing the oxygen content caused bysaid organic matter to 30 ppm or less;

[0014] 3. A method of producing a higher purity metal according toparagraph 1 or paragraph 2 above, wherein the coarse metal has a purityof 3N or less, the primary electrodeposited metal has a purity of 3N to4N excluding gas components such as oxygen, and the higher purity metalobtained by the secondary electrolysis has a purity of 4N to 5N or more;

[0015] 4. A method of producing a higher purity metal according toparagraph 1 or paragraph 2 above, wherein the coarse metal has a purityof 4N or less, the primary electrodeposited metal has a purity of 4N to5N excluding gas components such as oxygen, and the higher purity metalobtained by the secondary electrolysis has a purity of 5N to 6N or more;

[0016] 5. A method of producing a higher purity metal according to eachof paragraphs 1 to 4 above, wherein the electrolytic solution after thesecondary electrolysis step is used cyclically as the electrolyticsolution of the primary electrolysis;

[0017] 6. A method of producing a higher purity metal according to eachof paragraphs 1 to 5 above, wherein the electrolytic solution after theprimary electrolysis is either discharged outside the system or reusedafter refining the liquid;

[0018] 7. A method of producing a higher purity metal according to eachof paragraphs 1 to 6 above, comprising the step of electrolyzing thesecondary electrodeposited metal obtained in the secondary electrolysisstep as an anode or performing acid dissolution to the secondaryelectrodeposited metal in order to obtain a higher purity electrolyticsolution for tertiary electrolysis, and the step of further performingtertiary electrolysis by employing said higher purity electrolyticsolution for tertiary electrolysis with said secondary electrodepositedmetal as an anode;

[0019] 8. A method of producing a higher purity metal according to eachof paragraphs 1 to 7 above, wherein, among the higher purity metal, thetotal content of alkali metal elements such as Na, K is 1 ppm or less;the total content of radio active elements such as U, Th is 1 ppb orless; the total content of transition metal or heavy metal elements suchas Fe, Ni, Cr, Cu is 10 ppm or less; and the remaining portion thereofbecomes a higher purity metal or other indispensable impurities;

[0020] 9. A method of producing a higher purity metal according to eachof paragraphs 1 to 8 above, wherein the C content is 30 ppm or less andthe S content is 1 ppm or less; and

[0021] 10. A method of producing a higher purity metal according to eachof paragraphs 1 to 9 above, wherein the electrodeposited metal isfurther dissolved in a vacuum or dissolved under an Ar atmosphere or anAr—H₂ atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a diagram illustrating the outline of the primaryelectrolysis step, secondary electrolysis step, and the production stepof the electrolytic solution for the secondary electrolysis.

BEST MODE FOR CARRYING OUT THE INVENTION

[0023] The present invention is now described with reference to FIG. 1.FIG. 1 is a diagram illustrating the outline of the primary electrolysisstep, secondary electrolysis step, and the production step of theelectrolytic solution for the secondary electrolysis.

[0024] As shown in FIG. 1, a coarse material (3N or less, or 4N or less)metal 3 such as a metal scrap is placed in an anode basket 2 in theprimary electrolytic tank 1, and a primary electrodeposited metal isdeposited to a cathode 4 by electrolyzing the coarse metal material.Here, the initial electrolytic solution is prepared in advance. Purityof the primary electrodeposited metal pursuant to this primaryelectrolysis is 3N to 4N or 4N to 5N.

[0025] Next, the primary electrodeposited metal deposited to the cathode4 is electrolyzed as an anode 5 in the electrolytic tank 6 in order toobtain a secondary electrodeposited metal in a cathode 7.

[0026] In this case, the aforementioned primary electrodeposited metalas the anode 10 in a secondary electrolytic solution production tank 9is electrolyzed to produce the electrolytic solution 8. The cathode 11in this secondary electrolytic solution production tank 9 is insulatedwith an anion exchange membrane such that the metal from the anode 10 isnot deposited. Moreover, acid dissolution may be performed to theprimary electrodeposited metal in a separate container in order toconduct pH adjustment.

[0027] As depicted in FIG. 1, the electrolytic solution 8 produced asdescribed above is used in the secondary electrolysis. A higher purityelectrolytic solution can thereby be produced relatively easily, and theproduction cost can be significantly reduced. Further, the spentelectrolytic solution used in the secondary electrolytic tank 6 isreturned to the primary electrolytic tank 1 and used as the primaryelectrolytic solution.

[0028] The metal deposited to the cathode 11 in the secondaryelectrolytic tank 6 has a purity of a 5N level or 6N level.

[0029] When seeking a higher purity, or when the target purity could notbe obtained in the electro-refining process pursuant to the foregoingsecondary electrolysis, a tertiary electrolysis may be performed.

[0030] This step is similar to the case of the foregoing secondaryelectrolysis. In other words, a tertiary electrodeposited solution isproduced with the secondary electrodeposited metal deposited to thecathode in the secondary electrolysis as the anode of the tertiaryelectrolytic tank (not shown), or with the secondary electrodepositedmetal as the anode, and a tertiary electrodeposited solution isdeposited to the cathode of the tertiary electrolytic tank with thistertiary electrolytic solution as the electrolytic solution. The purityof the electrodeposited metal is sequentially improved as describedabove.

[0031] Similarly, the used tertiary electrolytic solution may be used asthe electrolytic solution of the secondary electrolytic tank or primaryelectrolytic tank.

[0032] The foregoing electrolytic solution may be entirelyliquid-circulated in the activated carbon tank in order to eliminateorganic matter in the higher purity metal aqueous solution. The oxygencontent caused by organic matter may thereby be reduced to 30 ppm orless.

[0033] The electro-refining of the present invention is applicable tothe electro-refining of metal elements such as iron, cadmium, zinc,copper, manganese, cobalt, nickel, chrome, silver, gold, lead, tin,indium, bismuth, gallium, and so on.

EXAMPLES AND COMPARATIVE EXAMPLES

[0034] Examples of the present invention are now described. TheseExamples are merely illustrative, and the present invention shall in noway be limited thereby. In other words, the present invention shallinclude all other modes or modifications other than these Exampleswithin the scope of the technical spirit of this invention.

Example 1

[0035] An electrolytic tank as shown in FIG. 1 was used to performelectrolysis with a 3N level massive iron as the anode, and a 4N leveliron as the cathode.

[0036] Electrolysis was implemented with a bath temperature of 50° C.,hydrochloric electrolytic solution at pH2, iron concentration of 50 g/L,and current density of 1 A/dm². Obtained thereby was electrolytic iron(deposited to the cathode) having a current efficiency of 90% and apurity level of 4N.

[0037] Next, this electrolytic iron was dissolved with a mixed solutionof hydrochloric acid and hydrogen peroxide solution, and made into anelectrolytic solution for secondary electrolysis by adjusting pH withammonia. Further, a second electrolysis (secondary electrolysis) wasimplemented with the 4N level primary electrolytic iron deposited to theforegoing cathode as the anode.

[0038] Conditions for the electrolysis are the same as those for theprimary electrolysis. Electrolysis was implemented with a bathtemperature of 50° C., hydrochloric electrolytic solution at pH2, andiron concentration of 50 g/L. As a result, obtained was electrolyticiron (deposited to the cathode) having a current efficiency of 92% and apurity level of 5N.

[0039] Analytical results of the primary electrolytic iron and secondaryelectrolytic iron are shown in Table 1. In the primary electrolyticiron, Al: 2 ppm, As: 3 ppm, Co: 7 ppm, Ni: 5 ppm, Cu: 1 ppm and Al: 2ppm existed as impurities. In the secondary electrolysis, however,excluding the existence of Co: 2 ppm, all other impurities were 1 ppm orless. Moreover, the used secondary electrolytic solution could bereturned to the primary electrolytic solution and used again.

[0040] As described above, superior results were yielded in that higherpurity (5N) iron was produced with two electrolytic refining processes,and the production of electrolytic liquid could be facilitated. TABLE 1(ppm) Impurity Al As B Co Cr Ni Raw Material   20   30   15  35    1  20 4N    2    3  <1  7  <1    5 5N  <1  <1  <1  2  <1    1 Impurity ZnCu Al O C N Raw Material   15   12   25 200   30   30 4N  <1    1    2 50   10   10 5N  <1  <1  <1  50   10 <10

Example 2

[0041] Similar to aforementioned Example 1, an electrolytic tank asshown in FIG. 1 was used to perform electrolysis with a 3N level massivecadmium as the anode, and titanium as the cathode.

[0042] Electrolysis was implemented with a bath temperature of 30° C.,sulfuric acid of 80 g/L, cadmium concentration of 70 g/L, and currentdensity of 1 A/dm². Obtained thereby was electrolytic cadmium (depositedto the cathode) having a current efficiency of 85% and a purity level of4N.

[0043] Next, this electrolytic cadmium was electrolyzed with a sulfatebath, and made into an electrolytic solution for secondary electrolysis.Further, a second electrolysis (secondary electrolysis) was implementedwith the 4N level primary electrolytic cadmium deposited to theforegoing cathode as the anode.

[0044] Conditions for the electrolysis are the same as those for theprimary electrolysis. Electrolysis was implemented with a bathtemperature of 30° C., sulfuric acid of 80 g/L, cadmium concentration of70 g/L, and current density of 1 A/dm². As a result, obtained waselectrolytic cadmium having a current efficiency of 92% and a puritylevel of 5N.

[0045] Analytical results of the primary electrolytic cadmium andsecondary electrolytic cadmium are shown in Table 2. In the primaryelectrolytic cadmium, Ag: 2 ppm, Pb: 10 ppm, Cu: 1 ppm and Fe: 20 ppmexisted as impurities. In the secondary electrolysis, however, excludingthe existence of Pb: 2 ppm and Fe: 3 ppm, all other impurities were 1ppm or less.

[0046] Moreover, similar to Example 1 above, the used secondaryelectrolytic solution could be returned to the primary electrolyticsolution and used again.

[0047] As described above, superior results were yielded in that higherpurity (5N) cadmium was produced with two electrolytic refiningprocesses, and the production of electrolytic liquid could befacilitated. TABLE 2 (ppm) Ag Pb Cu Zn Fe Raw Material 19 50 16 3 145 4N2 10 1 <1 20 5N <1 2 <1 <1 3

Example 3

[0048] Similar to aforementioned Example 1, an electrolytic tank asshown in FIG. 1 was used to perform electrolysis with a 3N level massivecobalt as the anode, and a 4N level cobalt as the cathode.

[0049] Electrolysis was implemented with a bath temperature of 40° C.,hydrochloric electrolytic solution at pH2, cobalt concentration of 100g/L, current density of 1 A/dm², and an electrolyzing time of 40 hours.Obtained thereby was approximately 1 kg of electrolytic cobalt(deposited to the cathode) having a current efficiency of 90%. Thepurity level thereof was 4N.

[0050] Next, this electrolytic cobalt was dissolved with sulfuric acid,and made into an electrolytic solution for secondary electrolysis byadjusting to pH with ammonia. Further, a second electrolysis (secondaryelectrolysis) was implemented with the 4N level primary electrolyticcobalt deposited to the foregoing cathode as the anode.

[0051] Conditions for the electrolysis are the same as those for theprimary electrolysis, and electrolysis was implemented with a bathtemperature of 40° C., hydrochloric electrolytic solution at pH2, andcobalt concentration of 100 g/L. As a result, obtained was electrolyticcobalt having a current efficiency of 92% and a purity level of 5N.

[0052] Analytical results of the primary electrolytic cobalt andsecondary electrolytic cobalt are shown in Table 3. In the raw materialcobalt, Na: 10 ppm, K: 1 ppm, Fe: 10 ppm, Ni: 500 ppm, Cu: 2.0 ppm, Al:3.0 ppm, Cr: 0.1 ppm, S: 1 ppm, U: 0.2 ppb, and Th: 0.1 ppb existed asimpurities. In the primary electrolysis, however, excluding theexistence of Fe: 5 ppm and Ni: 50 ppm, all other impurities were 0.1 ppmor less.

[0053] Further, in the secondary electrolysis, excluding the existenceof Fe: 2 ppm and Ni: 3 ppm, all other impurities were less than 0.1 ppm,thereby representing a significant decrease in impurities.

[0054] The used secondary electrolytic solution could be returned to theprimary electrolytic solution and used again.

[0055] As described above, superior results were yielded in that higherpurity (5N) cobalt was produced with two electrolytic refiningprocesses, and the production of electrolytic liquid could befacilitated. TABLE 3 (U, Th: ppb, Others: ppm) Na K Fe Ni Cu RawMaterial 10 1 10 500 2.0 Primary 0.1 <0.1 5 50 <0.1 Secondary <0.1 <0.12 3 <0.1 Al Cr S U Th Raw Material 3.0 0.1 1 0.2 0.1 Primary 0.1 <0.01<0.1 <0.1 <0.1 Secondary <0.01 <0.01 <0.1 <0.1 <0.1

Example 4

[0056] Similar to aforementioned Example 1, an electrolytic tank asshown in FIG. 1 was used to perform electrolysis with a 4N level massivenickel as the anode, and a 4N level nickel as the cathode.

[0057] Electrolysis was implemented with a bath temperature of 40° C.,hydrochloric electrolytic solution at pH2, nickel concentration of 50g/L, current density of 1 A/dm², and an electrolyzing time of 40 hours.Obtained thereby was approximately 1 kg of electrolytic nickel(deposited to the cathode) having a current efficiency of 90%. Thepurity level thereof was 5N.

[0058] Next, this electrolytic nickel was dissolved with sulfuric acid,and made into an electrolytic solution for secondary electrolysis byadjusting to pH with ammonia. Further, a second electrolysis (secondaryelectrolysis) was implemented with the 5N level primary electrolyticnickel deposited to the foregoing cathode as the anode.

[0059] Conditions for the electrolysis are the same as those for theprimary electrolysis, and electrolysis was implemented with a bathtemperature of 40° C., hydrochloric electrolytic solution at pH2, andnickel concentration of 50 g/L. As a result, obtained was electrolyticnickel having a current efficiency of 92% and a purity level of 6N.

[0060] Analytical results of the primary electrolytic nickel andsecondary electrolytic nickel are shown in Table 4. In the raw materialnickel, Na: 16 ppm, K: 0.6 ppm, Fe: 7 ppm, Co: 0.55 ppm, Cu: 0.62 ppm,Al: 0.04 ppm, Cr: 0.01 ppm, S: 1 ppm, U: 0.2 ppb, and Th: 0.1 ppbexisted as impurities. In the primary electrolysis, however, excludingthe existence of Fe: 2 ppm and Co: 0.2 ppm, all other impurities were0.1 ppm or less.

[0061] Further, in the secondary electrolysis, only Fe: 0.2 ppm existed,and all other impurities were less than 0.1 ppm, thereby representing asignificant decrease in impurities. The used secondary electrolyticsolution could be returned to the primary electrolytic solution and usedagain.

[0062] As described above, superior results were yielded in that higherpurity (6N) nickel was produced with two electrolytic refiningprocesses, and the production of electrolytic liquid could befacilitated. TABLE 4 (U, Tb: ppb, Others: ppm) Na K Fe Co Cu RawMaterial 16 0.6 7 0.55 0.62 Primary 0.1 <0.1 2 0.2 <0.1 Secondary <0.1<0.1 0.2 <0.1 <0.1 Al Cr S U Th Raw Material 0.04 0.01 1 0.2 0.1 Primary<0.01 <0.01 <0.1 <0.1 <0.1 Secondary <0.01 <0.01 <0.1 <0.1 <0.1

Example 5

[0063] A 4N level raw material cobalt differing from the cobalt usedabove was used to perform a separate primary electrolysis and secondaryelectrolysis, and, thereupon, the electrolytic solution was circulatedin the activated carbon tank in order to eliminate the organic matter inthe higher purity metal aqueous solution. The analytical results of theimpurity elements obtained pursuant to the aforementioned refining areshown in Table 5.

[0064] As impurities contained in the electrolytic cobalt pursuant tothe foregoing primary electrolysis and secondary electrolysis, only Ti:1.8 ppm, Fe: 1.3 ppm and Ni: 4.2 ppm existed as impurities exceeding 1ppm, and, excluding gas components such as oxygen, all other impuritieswere less than 0.1 ppm, thereby representing a significant decrease inimpurities.

[0065] The used secondary electrolytic solution could be returned to theprimary electrolytic solution and used again. Although not shown inTable 5, oxygen was significantly eliminated with activated carbon, andwas reduced to 30 ppm or less.

[0066] As described above, superior results were yielded in that higherpurity (5N) cobalt was produced with two electrolytic refiningprocesses, and the production of electrolytic liquid could befacilitated. TABLE 5 Content: ppm (weight) Element Content ElementContent Element Content Li <0.005 As 0.03 Sm <0.005 Be <0.005 Se <0.05Eu <0.005 B <0.01 Br <0.05 Gd <0.005 F <0.05 Rb <0.005 Tb <0.005 Na<0.01 Sr <0.005 Dy <0.005 Mg <0.005 Y <0.001 Ho <0.005 Al 0.13 Zr <0.005Er <0.005 Si 0.03 Nb <0.01 Tm <0.005 P 0.3 Mo 0.12 Yb <0.005 S 0.17 Ru<0.01 Lu <0.005 Cl 0.05 Rh <0.01 Hf <0.005 K <0.01 Pd <0.05 Ta <1 Ca<0.05 Ag <0.01 W <0.05 Sc <0.001 Cd <0.05 Re <0.01 Ti 1.8 In <0.01 Os<0.005 V <0.001 Sn <0.01 Ir <0.01 Cr 0.32 Sb <0.01 Pt <0.01 Mn <0.01 Te<0.05 Au <0.05 Fe 1.3 I <0.01 Hg <0.05 Co Matrix Cs <0.01 Ti <0.01 Ni4.2 Ba <0.05 Pb <0.01 Cu 0.05 La <0.1 Bi <0.005 Zn 0.03 Ce <0.005 Th<0.0001 Ga <0.05 Pr <0.005 U <0.0001 Ge <0.1 Nd <0.005

[0067] Effect of the Invention

[0068] As described above, superior characteristics are yielded in thatthe primary electrodeposited metal as an anode is electrolyzed in orderto produce a secondary electrolytic solution, and, further, by usingsuch primary electrodeposited metal as the secondary electrolytic anode,higher purity electro-refining of 5N to 6N level is realized in additionto enabling the reduction of production costs of the secondaryelectrolytic solution of 4N to 5N level.

[0069] Moreover, a further superior effect is yielded in that the spentelectrolytic solution used in the secondary electrolytic tank isreturned to the primary electrolytic tank and may be used as the primaryelectrolytic solution, whereby the oxygen content can be reduced to 30ppm or less.

1. A method of producing a higher purity metal comprising the step ofelectrolyzing a coarse metal material by primary electrolysis to obtaina primary electrodeposited metal, the step of performing electrochemicaldissolution with the primary electrodeposited metal obtained in theprimary electrolysis step as an anode or performing acid dissolution tothe primary electrodeposited metal in order to obtain a higher purityelectrolytic solution for secondary electrolysis, and the step offurther performing a secondary electrolysis by employing said higherpurity electrolytic solution for secondary electrolysis with saidprimary electrodeposited metal as an anode.
 2. A method of producing ahigher purity metal comprising the step of electrolyzing a coarse metalmaterial by primary electrolysis to obtain a primary electrodepositedmetal, the step of obtaining a higher purity electrolytic solution forsecondary electrolysis by performing electrochemical dissolution or aciddissolution with the primary electrodeposited metal obtained in theprimary electrolysis step as an anode, and the step of furtherperforming a secondary electrolysis by employing said higher purityelectrolytic solution for secondary electrolysis with said primaryelectrodeposited metal as an anode, wherein said electrolytic solutionis liquid-circulated in an activated carbon tank in order to eliminateorganic matter in the higher purity metal aqueous solution, therebyreducing the oxygen content caused by said organic matter to 30 ppm orless.
 3. A method of producing a higher purity metal according to claim1 or claim 2, wherein the coarse metal has a purity of 3N or less, theprimary electrodeposited metal has a purity of 3N to 4N excluding gascomponents such as oxygen, and the higher purity metal obtained by thesecondary electrolysis has a purity of 4N to 5N or more.
 4. A method ofproducing a higher purity metal according to claim 1 or claim 2, whereinthe coarse metal has a purity of 4N or less, the primaryelectrodeposited metal has a purity of 4N to 5N excluding gas componentssuch as oxygen, and the higher purity metal obtained by the secondaryelectrolysis has a purity of 5N to 6N or more.
 5. A method of producinga higher purity metal according to each of claims 1 to 4, wherein theelectrolytic solution after the secondary electrolysis step is usedcyclically as the electrolytic solution of the primary electrolysis. 6.A method of producing a higher purity metal according to each of claims1 to 5, wherein the electrolytic solution after the primary electrolysisis either discharged outside the system or reused after refining theliquid.
 7. A method of producing a higher purity metal according to eachof claims 1 to 6, comprising the step of electrolyzing the secondaryelectrodeposited metal obtained in the secondary electrolysis step as ananode or performing acid dissolution to the secondary electrodepositedmetal in order to obtain a higher purity electrolytic solution fortertiary electrolysis, and the step of further performing tertiaryelectrolysis by employing said higher purity electrolytic solution fortertiary electrolysis with said secondary electrodeposited metal as ananode.
 8. A method of producing a higher purity metal according to eachof claims 1 to 7, wherein, among the higher purity metal, the totalcontent of alkali metal elements such as Na, K is 1 ppm or less; thetotal content of radio active elements such as U, Th is 1 ppb or less;the total content of transition metal or heavy metal elements such asFe, Ni, Cr, Cu is 10 ppm or less; and the remaining portion thereofbecomes a higher purity metal or other indispensable impurities.
 9. Amethod of producing a higher purity metal according to each of claims 1to 8, wherein the C content is 30 ppm or less and the S content is 1 ppmor less.
 10. A method of producing a higher purity metal according toeach of claims 1 to 9, wherein the electrodeposited metal is furtherdissolved in a vacuum or dissolved under an Ar atmosphere or an Ar—H₂atmosphere.